In this study, the mercury (Hg) speciation and mass distribution at two cement plants located in northern and eastern Taiwan were investigated. Gaseous Hg in the kiln flue gas was sampled by the Ontario Hydro method, and the solid samples were collected to analyze the Hg mass balance. The total Hg concentrations in the raw mill electrostatic precipitator (ESP) input of the two plants were 155.70 and 64.62 µg Nm–3, respectively, which were higher than those at any other sampling point. Approximately 97.5 and 86.5% of the Hg in the raw mill ESP input at Plants 1 and 2, respectively, was particle-bound. Elemental Hg was the major gaseous Hg species emitted into the atmosphere from these two cement plants, accounting for 56.4 to 98.2% of the total Hg in the flue gas. The total Hg mass output was calculated to be 61.374 and 204.596 mg-Hg per metric ton-clinker (mg ton–1) for cement Plants 1 and 2, respectively. The Hg emission factors for Plants 1 and 2 were thus 0.059 and 0.196 g-Hg per metric ton-cement (g ton–1), respectively. These results improve our understanding of Hg emissions from cement plants in Taiwan and provide useful information for selecting Hg control technology.